Most workplaces have signs for safety or practical reasons.  Signs are used to point out hazards and exits and to provide information.   Why not liven things up with some funny signs to brighten your work day.  As long as your boss is OK with it, there is no harm in some innocent humour in the workplace.

Everyone says that laughter is the best medicine, so why not give more funny gifts?  It certainly brightens your day when you receive a funny gift.  So turn the table and make sure you give funny gifts too...